A bipolar junction transistor (BJT) is a three-terminal device. The three terminals include a base terminal, a collector terminal, and an emitter terminal. BJTs are formed by two p-n junctions placed back-to-back in close proximity to each other, with one of the regions common to both junctions. There is a first junction between the base and the emitter, and a second junction between the emitter and the collector. This forms either a p-n-p or n-p-n transistor depending upon the characteristics of the semiconductive materials used to form the BJT. The terminals of the BJT are connected to their respective base, collector, and emitter. In BJTs, the current flow through the emitter and collector terminals is controlled by the voltage across the base and emitter terminals. Various techniques have been implemented to improve transistor device performance. For example, hetereojunction bipolar transistors (HBT) have been fabricated. HBTs are BJTs where the emitter-base junction is formed from two different semiconductive materials having similar characteristics. Because the HBTs are formed of two different semiconductor materials, the energy band gaps, as well as other material properties, can be different in the emitter, base, and collector. Accordingly, improved transistor device performance is achieved, such as higher cut-off frequency values. However, although existing approaches have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects.